The Original Sisters

As you know the Mikaelson family are Original Vampires, right? Well, how did Esther know the spell of immortality will work? We don't know but here is a story that will answer all of these questions I stated.
The two main characters are bestfriends for life but when their friends' mother needs help with an experiment in excluding dark magic; one of them decides to help her out. The other one being the overprotective sister she is; ends up following them. Once the witches started setting up, she realizes that her dumb little sister is going to do something she will regret. But before she and her other bestfriend could stop Ester, it was too late.